Search results for "Cristallography"
showing 10 items of 65 documents
Structure of rat odorant-binding protein OBP1 at 1.6 angstrom resolution
2009
The nasal mucosa is a specialist interfacial region sandwiched between the olfactory system and the gaseous chemical milieu. In mammals and insects, this region is rich in odorant-binding proteins that are thought to aid olfaction by assisting mass transfer of the many different organoleptic compounds that make up the olfactory landscape. However, in mammals at least, our grasp on the exact function of odorant-binding proteins is tentative and better insight into the role of these proteins is warranted, not least because of their apparent significance in the olfactory systems of insects. Here, the crystal structure of rat odorant-binding protein 1 is reported at 1.6 Å resolution. This prote…
Trimeric HIV Env provides epitope occlusion mediated by hypervariable loops
2014
AbstractHypervariable loops of HIV-1 Env protein gp120 are speculated to play roles in the conformational transition of Env to the receptor binding-induced metastable state. Structural analysis of full-length Env-based immunogens, containing the entire V2 loop, displayed tighter association between gp120 subunits, resulting in a smaller trimeric diameter than constructs lacking V2. A prominent basal quaternary location of V2 and V3′ that challenges previous reports would facilitate gp41-independent gp120-gp120 interactions and suggests a quaternary mechanism of epitope occlusion facilitated by hypervariable loops. Deletion of V2 resulted in dramatic exposure of basal, membrane-proximal gp41…
5-(3,4-Dimethoxybenzyl)-7-isopropyl-1,3,5-triazepane-2,6-dione acetonitrile solvate refined using a multipolar atom model
2010
International audience; The crystal structure of the title compound, C16H23N3O4·CH3CN, was refined using a multipolar atom model transferred from an experimental electron-density database. The refinement showed some improvement in crystallographic statistical indices compared with the independent atom model. The triazepane ring adopts a twist-boat conformation. In the crystal structure, the molecule forms intermolecular contacts with 14 different neighbours. There are two N-H...O and one C-H...O intermolecular hydrogen bond.
Synthesis and characterization of [Mo(μ-EPh)(CO)3(CH3CN)]2 (E=Se, Te), including the X-ray structure of the tellurium derivative
2000
International audience; The reaction of Mo(CO)3(MeCN)3 and E2Ph2 (E=Se, Te) yields the edge-sharing bioctahedral, metalmetal bonded Mo(I) products [Mo(CO)3(MeCN)(μ-EPh)]2. The structure of the tellurolato derivative was confirmed by X-ray crystallography: triclinic, space group , a=7.3149(17), b=9.6959(16), c=9.7090(10) Å, α=80.366(10), β=76.563(13), γ=72.877(16)°, V=636.43(19) Å3, Dcalc=2.222 Mg m−3, μ=3.271 mm−1, R1=0.0418, wR2=0.0689 for 163 parameters and 2238 data with I>2σ(I). The interaction of these compounds with excess E2Ph2 as a possible entry to homoleptic Mo(EPh)3 has been investigated.
Cyclopentadienylmolybdenum(VI) and molybdenum(V) oxo chemistry: New synthetic and structural features
2002
International audience; Convenient syntheses for Cp, Cp*, and related cyclopentadienyl derivatives (4Cp = C5HiPr4; Cp′′′ = C5H2tBu3-1,2,4) of formula [(Ring)2Mo2O5] are described. Compound [Cp2Mo2O5] was produced in good yields by the rapid oxidation of red [CpMoO2]4 with PhIO in CH2Cl2. [Cp*2Mo2O5] was obtained by CH3COOH acidification of aqueous solutions of [Cp*MoO3]−Na+, the latter being generated in a single step from [Cp*MoCl4] and more than 5 equiv. of aqueous NaOH in air. Minor quantities of [Cp*MoO2]2 were also isolated from this reaction, although the formation of this by-product may be reduced by using a two-step basic hydrolysis procedure. Extension of the latter strategy also a…
Differences between Bond Lengths in Biogenic and Geological Calcite
2010
8 pages; International audience; We used high-resolution neutron powder diffraction to accurately measure the atomic positions and bond lengths in biogenic and geological calcite. A special procedure for data analysis was developed in order to take into account the considerable amounts of magnesium present in all the investigated samples. As a result, in biogenic calcite we found some atomic bonds to have significantly different lengths as compared to those in geological calcite, after the contribution of magnesium is accounted for. The maximum effect (elongation up to 0.7%) was found for the C−O bonds. We also analyzed changes in frequencies and spectral widths of normal vibrations of carb…
Magneto-structural and theoretical study of the weak interactions in a Mn(II) complex with a very unusual N,O-chelating coordination mode of 2-aminot…
2017
International audience; The Mn(II) complex {[Mn(atpa)(H2O)2]·H2O}n (1),with the dicarboxylate ligand 2-aminoterephthalic acid (H2atpa), has been synthesized and crystallographically, spectroscopically and magnetically characterized. Complex 1 shows a very unusual 1κ2N,O coordination mode of the aminoterephthalate dianion with the Mn(II) ion. One of the carboxylate groups shows a syn-anti-μ2-η1:η1 binding mode to form a 2D square grid. The magnetic properties of this compound can be very well reproduced with a regular S = 5/2 chain model with a very weak antiferromagnetic coupling constant of J = −0.2 cm−1 through the single syn-anti carboxylate bridges. EPR measurement also supports the exp…
Polymorphism in a π stacked Blatter radical: structures and magnetic properties of 3-(phenyl)-1-(pyrid-2-yl)-1,4-dihydrobenzo[ e ][1,2,4]triazin-4-yl
2020
International audience; 3-(Phenyl)-1-(pyrid-2-yl)-1,4-dihydrobenzo[e][1,2,4]triazin-4-yl (2) demonstrates the first example of polymorphism in the family of Blatter radicals. Two polymorphs, 2α and 2β, have been identified and characterized by single crystal X-ray diffractometry and magnetic susceptibility measurements to investigate their magnetism–structure correlations. Both polymorphs form one-dimensional (1D) π stacks of evenly spaced radicals with distinctly different π–π overlap modes. Within the 1D π stacks, radicals are located at evenly interplanar distances, 3.461 Å for 2α and 3.430 Å for 2β. Magnetic susceptibility studies indicate that both polymorphs exhibit antiferromagnetic …
Synthesis of ortho-fonctionnalized arylphosphines and their applications
2020
This thesis reports with the synthesis of ortho-functionnalized phosphines bearing phosphonium and 1,2,3-triazole moieties.The synthesis of phosphines-phosphoniums, using as key-step Phospha-Fries rearrangement and Appel reaction is described. Eight new phosphines- phosphoniums, bearing aryl, alkyl or ferrocenyl fragments on the phosphonium part, have been prepared with overall yields reaching 48%. These phosphines- phosphoniums have been used in the preparation of gold (I) complexes which have been characterized using spectroscopic methods and X ray diffraction. Both gold (I) complexes and phosphines-phosphoniums have been studied in biology and these compounds turned out to be cytotoxic i…
PI-Extension of porphyrins via intramolecular aromatic oxidative C-N coupling
2019
Π-extension of porphyrins has been performed via intramolecular oxidative C-N coupling of peripheral pyridinyl fragment(s) with the porphyrin core. These fusion reactions lead to the formation of C-N bond(s) between the substituent(s) and the porphyrin. The precursors were functionnalized with 2-mercaptopyridine, 8-hydoxyquinoline and 2-picoline at their meso or β-pyrrolic positions via aromatic nucleophlic substitution, cross-coupling reaction or reaction of the macrocycle with organolithium reagents. Voltametric analyses revealed some marked differences on the reactivity of the porphyrins depending on their substitution pattern and metalation (nickel(II) or zinc(II)). Chemical and electro…